Adjustable clamp



Dec. 20, 1966 B. N. SVENSON ADJUSTABLE CLAMP 3 Sheets-Sheet 1 Filed July 27, 1964 INVENTOR. BERT N. SVENSON ATTORNEY Dec. 20, 1966 B. N. SVENSON 3,292,812

ADJUSTABLE CLAMP Filed July 27, 1964 w 3 Sheets-Sheet 2 INVENTOR. BERT N. SVENSON TTO/QNEY Dec. 20, 1966 B. N. SVENSON ADJUSTABLE CLAMP 3 Sheets-Sheet 3 INVENTOR. BERT N. SVENSON BY yr AT TORNE) Filed July 27, 1964 United States Patent The invention relates to adjustable clamps and more particularly to cam clamps that lock by over-center action.

There is a wide variety of clamps available to users whose purpose is to hold down work being processed or to clamp a cover to a pressure vessel so that the closed vessel is sealed. In the case of vessels, the clamps are conventionally used in pluralities and spaced an equal distance apart around the cover of the vessel. The clamps bear upon the cover so that the cover is thrust upon the rim of the vessel opening or a sealing gasket about the opening. Conventional vessel cam clamps comprise eye bolts or other threaded members secured to the outer wall of the pressure vessel and which protrude upwardly above the outer rim of the cover through notches in the cover rim with the camming elements threadably engaged by the bolt. The cover area about the notch comprises a bearing surface against which camming elements of the clamp bear to urge the cover toward sealing relationship with the opening of the vessel.

Clamps utilized for holding Work (such as metal sheets or plate) in place upon a rest or support surface conventionally have a clamp strap against which the cam surfaces of the clamp bear, urging the strap into holding relationship against the plate or sheet. Such straps may be either single end or double end straps, depending on the usage. The bolt of the clamp may extend through the strap and be secured to the work rest. Alternatively, the cam or cams of the clamp may elevate or depress an end of the clamp strap to lever the strap into binding relationship against the work.

One problem that arises is the necessity for fine adjustment of clamping pressure exerted by cam surfaces which are brought into position against the work to hold it securely. conventionally, the clamp cam is adjustably mounted to the eye bolt since the cam must be displaced along the eye bolt a distance after cam release in order to clear the edges of the cover notches when the eye bolt and clamp cams are pivoted away from the cover rim or other workpiece. It is also necessary to adjust the clamping member back along the bolt and into engaging orientation with the bearing surfaces of the work prior to operating the clamp cam to achieve final clamping.

Most clamps of this type operate on a toggle principle in which the final clamping position of the clamp member is over center (slightly past the point of greatest pressure) so that the resultants of the clamping forces tend to keep the clamping member in a locked position. A handle that may be detachable and affording leverage is utilized with the clamping member to achieve this toggled or over-center position. If a coarse threaded eye bolt is used, it is commonly very difficult to achieve proper clamping. The clamp must be rotated one full turn to bring the cam into place. The 360 rotation of the clamp about the eye bolt results in too great a displacement of the clamp with respect to the ultimate position of the work with respect to the work bed, or the ultimate position of the cover with respect to the pressure vessel. It often happens that the lead of the thread is great enough that the clamp cannot be closed in one position and yet is too loose when the thread is backed off one turn. A finer thread pitch may solve this problem, but a finer thread has less holding power than the comparable coarse thread.

. I have invented a simple yet eifective clamping mechanism which may be utilized with either a coarse or a orientation is also changed fine thread and permits clamping force adjustment not possible with other screw adjusted clamps. The invention contemplates an adjustable cam clamp that comprises a threaded member secured by pivot means to the work rest of a workpiece. A cam lobe is engaged with the threaded member and is rotatable about an axis transverse to the long axis of the threaded member. The cam lobe has diametrically opposed first and second cam surfaces each adapted to urge a workpiece into clamping relationship with the work rest. Handle means adapted to turn the lobe about the transverse axis and means limiting the turning of the lobe are preferably part of a handle mount fixed to the cam lobe. The cam lobe is threadably displaceable with respect to the work rest along the axis of the threaded member and also rotatable with respect to the long axis of the threaded member. Thus the cam lobe may be moved to and from the workpiece and also shifted to opposite orientation with respect to the threaded member. The cam lobe being rotatable about the transverse axis, either the first or the second cam surface of the lobe may be brought into clamping relationship with the workpiece. Thus the cam lobe may be displaced from the work by turning about the threaded member 180, and the lobe turned about the transverse axis 180 to clamp the Work with the other cam surface to achieve one-half the thread pitch adjustment.

The distance from the transverse axis to the first surface of the cam lobe may differ from the like distance of the second surface by an increment related to the pitch of the thread of the threaded member if an alternative adjustment of less than one-half the thread pitch is desired. For instance, the first surface of each lobe may be further displaced from the transverse axis than the second surface by one-quarter the thread pitch. This differential enables quarter-thread adjustment of the clamping position of the cam clamp for one direction of rotation about the threaded member and three-quarters of the thread pitch adjustment for opposite rotation. Other adjustment increments may be provided by variation of the characteristics set forth in the above description.

Preferably, the first and second surfaces are diametrically opposed and the rest of the cam lobe shaped so that the surfaces may be smoothly moved into contact with the workpiece.

The workpiece may be a pressure vessel cover and the work rest a pressure vessel. Alternatively, the work rest may be a bench and the workpiece a clamp strap adapted to bind a sheet or plate or other object to be worked upon.

The adjustable clamp of the invention may comprise a cam arbor mounting an identical cam lobe at each end secured to the threaded member. It is utilized by bringing the cam arbor and lobes into approximate clamping position with respect to the workpiece. The cam arbor is then turned about the long axis of the threaded member to displace the lobes toward the workpiece. The handle means is used to turn the first or the second surface of the spaced cam lobes to clamp against the workpiece as desired. If the first selected surfaces do not result in desired clamping, the cam arbor and the lobes may be rotated about the axis of the threaded member one-half turn. This, of course, affects the spacing between the lobes and the workpiece. The handle mount The handle may then be turned to rotate the lobes about the cam arbor axis and invert the lobes such that the other camming surface of each lobe bears against the workpiece. If the distance from the cam arbor axis to the first cam surface and to the second cam surface is identical, a distance adjustment of the clamping position equal to one-half the thread lead is accomplished by 180 rotation of the arbor about the threaded member. If the surface displacements differ by an increment equal to the thread lead a half-tum of the cam arbor results in either a one-half or a one and onehalf thread lead adjustment, depending upon the direction of rotation. Thus a half-turn of the cam arbor permits selection of the cam surface which contacts the cover and adjustment of the clamping pressure related to the displacement dilferential between the first and second cam surfaces of a lobe.

When thecam arbor is turned 180 about the eye bolt the position of the handle mount is, of course, changed between inboard of the cover rim and outboard of the cover rim. However, when the cam lobes are inverted to achieve selection of the proper first or second cam surface, the handle mount is again brought into clamping relationship to the cover.

The handle mount may have many configurations, depending upon the shape of the vessel cover. If the cover is domed, precluding use of a handle which protrudes horizontally from the mount, the handle mount may include means for operationally accepting a handle so that the handle extends vertically from the mount in either of the 180 displacements of the handle mount.

These and other advantages of the invention are apparent from the following detailed description and drawing in which like parts bear like reference numerals and in which:

FIG. 1 is a fragmentary plan view of a pressure vessel having clamps in accordance with the invention;

FIG. 2 is a fragmentary sectional elevation taken along line 22 of FIG. 1;

FIG. 3 is a fragmentary planview showing a clamp adjusted 180 from the position shown .in FIG. 1;

FIG. 4 is a fragmentary sectional elevation taken along line 44 of FIG. 3; v

FIG. 5 is a view similar to FIG. 4 showing the cams of the adjustable cam clamp returned to clamping position after being inverted;

FIG. 6 is a fragmentary sectional elevation of an alternate embodiment of the invention;

FIG. 7 is an elevational view taken along line 7-7 of FIG. 6 and partly broken away;

FIG. 8 is a further alternate embodiment of the invention illustrating a handle mount;

FIG. 9 is a fragmentary plan view taken along line 99 of FIG. 8;

FIG. 10 is an alternate embodiment of the invention in which the workpiece comprises a clamp strap adapted to hold .a metal sheet;

FIG. 11 is a further alternate embodiment of the invention including a double-ended clamp strap; and

FIG. 12 is a sectional elevation detailing an alternate clamp embodiment.

In FIGS. l-3 a pressure vessel 10 of substantially cylindrical configuration having a vessel wall 11 and a domed cover 12 is held closely by a plurality of evenly spaced adjustable clamps 13, 14, 15. The clamps are substantially identical over-center cam devices which, when closed as shown, urge cover 12 into clamping relationship with a sealing gasket 16. The gasket is interposed between the rim 17 of an opening 18 of the vessel wall and a gasket groove 19 on the underside of the vessel cover.

The cover hinges on a pin 21 of a hinge bracket 22 fixed to wall 11 opposite a cover handle 24. A plurality of tabs 26, each of which protrudes beyond an outer rim 27 of the cover, have notches 29 through which threaded members or eye bolts 31 of the clamps extend.

Each eye bolt 31. of a clamp has a threaded portion 32 and an eye loop 33. A plurality of pivot mounts 34 each comprising two spaced ears 35 and a pivot pin 37 is fixed to the exterior wall of the vessel adjacent the opening of the vessel. Each clamp eye bolt is pivotally mounted on a pivot pin that passes through eye loop 33 of the particular eye bolt. The orientation of the pivot pin is such that the eye bolt of each clamp may be pivoted out- Wardly in notch 29 away from rim 27. of the cover, to. re

move the clamp from engagement with the cover.

A cam arbor 41 is threadably engaged with threaded.

portion 32 of each eye bolt. The cam arbor is substantially cylindrical and is adapted to rotate about the long 42 threadably mounted within an end of the cam arbor may lock the cam arbor in position with respect to the eye bolt once proper adjustment is made. The cam arbor has a long axis 43 transverse to the axis of the eye bolt.

Each end of the cam arbor journals a cam lobe. A cam lobe 44 is on one side of the eye bolt and a cam lobe 45 is on the opposite side of the eye bolt. The cam lobe-s are substantially identical. A handle mount 47 rigidly connects the two cam lobes and is preferably integrally formed therewith such that a clearance slot 48 is defined between the facing sides of the cam lobes. A cylindrical hole 49 extends through the handle mount substantially parallel to a long axis 50 of the cam lobes. A reduced diameter stub 51 of a handle 52 may be removably lodged In FIG. 2, the upper and lower handle mount surfaces 1 adjacent hole 49 are seen to be charnfered, forming contact shoulders 54, 55 on the handle mount. Contact surface 55 rests against the upper surface of cover 12,1acting as 'a limit stop controlling the rotation of the cam These 1 lobes with respect to axis 43 of the cam arbor. relationships are shown in more detail in FIG. 5. In FIG. 5 eye bolt 31 is broken away so that the typical clamping position of the cam lobes with respect to the 1 cam contacting surface 12A of the cover area adjacent 1 each notch 29 may be seen. In both FIGS. 4 and 5 the long axis 56 of the eye bolt is substantially vertical, as

the eye bolt extends upwardly through the notch'on the 1 cover in cover-clamping position. Cam lobe 44 has a first cam surface 57 and a diametrically opposed second 1 cam surface 58. In FIG. 5 second cam surface 58 bears against cam contacting surface 12A at a point slightly off center with respect to axis 56 of the eye boltthe locked clamping position of the cam lobes.

Preferably cam surfaces 57 and 58 define the greatest 1 projection of the cam lobe periphery 59 from arbor axis 43. Therefore, the greatest clamping pressure'is exerted when either these surfaces contact the cover.

The radial distance of surface 57 from the arbor axis is indicated by the dimension D. A like dimension for 1 cam surface 58 is indicated by dimension E. These dimensions may be identical, in which case the clamp assembly affords adjustment of clamping force in distance. increments equal to one-half the thread pitch of the, eye 1 bolt. Alternatively, the radial distances may differ by an increment related to the thread pitch, in which case the amount of fine linear adjustment occurring with each 1 rotation of the cam lobes about axis 56 of the eye bolt may be a fraction of the thread pitch either added 1 to or subtracted from the half pitch displacement.

In FIG. 4 cam surface 58 is oriented remote from cam 1 contacting surface 12A. By reversing handle 52 within handle mount hold 49 the cam lobes may be rotated about the cam arbor into the clamping position shown in FIG.

5. As the cam lobes rotate about arbor axis 43, surface 58 passes over-center with respect to bolt axis 56 an amount controlled by contact surface 55. Because of the conventional over-center relationship the cam lobes can- I not counter-rotate and the clamp is locked in position.

Coarse adjustments in clamping position are made byremoving the cam lobes from over-center position so that no surface of the lobes contacts cover 12 and rotating the lobes and the cam arbor about axis 56 the number of threads desired in either direction on the eye bolt. Handle 52 is then used to rotate the cam lobes back into clamping position. If finer adjustment is necessary, the lobes are unclamped and the arbor rotated 180, which puts the cam lobes and handle mount in position of FIG. 4. Then the handle is reversed in the mount and the lobes rotated about the arbor axis back into over-center clamping position.

The apparatus of the invention provides for a choice of which of the opposed cam surfaces implements the clamping. Because of this facility, almost any desired degree of clamping pressure differential may be achieved by proper manipulation of the lobes about the axes 43 and 56. Conventional devices require removing pivot pin 37 to change the position of the cam arbor on the eye bolt' because they cannot change the relationship of the arbor and lobes to the cover.

An alternate embodiment of the invention shown in FIGS. 6 and 7 reverses the threaded engagement of the eye bolt. The clamp illustrated therein comprises an eye bolt 61 having a lower threaded portion 62 threadably engaged with a pivot pin 64 journalled in each of the spaced ears 65, 66 of a pivot mount assembly 67. The pivot mount is secured as by welding to cylindrical wall 11 of a pressure vessel 10. Domed cover 12 is in place over the opening of the pressure vessel. Conventional notched tabs 68 extend from outer rim 27 of the cover, as shown in FIG. 6. A contoured contact area 69 on the outer upper surface of the tab on each side of the notch is adapted for clamping relationship with one of substantially identical cam lobes 71, 72. The cam lobes are mounted upon opposite ends of a cam arbor 74 which extends through eye loop 75 of eye bolt 61. Pins, such as roll pins 77, confine the cam lobes to the cam arbor. The lobes may rotate about the cam arbor periphery. Alternatively, the lobes may be fixed to the cam arbor which must then be rotatable within the eye loop.

Each cam lobe has diametrically opposed cam surfaces 79, 80 adapted to bear upon a contact area 69. One side of each cam periphery is flattened at 82 for clearance. The other side of each cam lobe is fixed to a handle boss 83 from which a handle 84 protrudes. The lobes, boss and handle may be of one piece construction.

The embodiment of FIGS. 6 and 7 is comprised so that handle 84 extends beyond the cover rim when the clamp is locked. Such positioning is desirable when the dome 12C of the cover is extremely convex. Opposite contact surfaces 86, 87 on the handle boss are adapted to limit rotation of the cam lobes by the contact of one or the other with limit surface 89 of the cover tab. Rotation is halted once the cam surfaces of the cam lobes have passed eye bolt axis 56 sufficiently to lock in over-center position.

The operation of the cam clamp illustrated in FIGS. 6 and 7 is similar to that described for the embodiment of FIGS. 1-5 with the exception of the handle orientation. Other handle and handle mount variations within the scope of the invention will be dictated by the configuration of the cover and the positioning of the clamps with respect to other impedimentia of the pressure vessel.

A clamp 91 in accordance with the invention is illusstrated in FIGS. 8 and 9. The clamp differs from those previously described in that it comprises elements limiting outward pivotal motion of the clamp until certain cover orientations are achieved. Clamp 91 has an eye bolt 31 with an upper threaded portion 32 and a lower eye loop 33. A pivot mount 34 on the vessel journals an elon gated pivot pin 92 to which the eye loop is fixed by means of one or more set screws 93. A flat cover 94 is in sealing relationship upon the pressure vessel 10. Notched tabs 95 extend from the cover rim at intervals around the cover. The handle 96 may intervene between two tabs, as shown in FIG. 9. Conventionally, the handle is opposite a cover hinge (not shown) about which the cover pivots and which limits displacement of one side of the cover from the vessel opening.

' Stop ribs 98 spaced outwardly from rim 27 of the cover 6 extend between notched tabs and handle 96. An inboard surface 99 of each rib is substantially vertical and is adapted to engage a limit arm 101 fixed in or to an extending portion 103 of pivot pin 92. Limit arm 101 thus moves in synchronism with the pivotal motion of the cam clamp toward and away from the cover tab. As shown by the dotted lines of FIG. 8, limit arm 101 contacts stop rib 98 and precludes further outward motion of the clamp while the cover is still seated upon the pressure vessel. In the position shown the cam lobes prevent substantial upward movement of the cover, such as might occur if internal pressures within the vessel are suddenly released. The combination of elements shown in FIGS. 8 and 9 prrovides a safety check preventing injury to personnel manipulating the clamps should the cover explode from the vessel.

The limiting action of the arm is defeated by lifting the cover manually from wall 11 so that the vessel may exhaust between the cover and the wall before the clamps are swung outwardly free of the cover. The area of engagement between the top of limit arm 101 and stop surface 99 is such that the cover must be lifted the requisite distance before the clamp may be outwardly displaced.

If the cover is not hinged to the vessel it is desirable to use limiting clamps at diametrically opposed points on the cover rim to prevent sudden displacement of the cover at one side.

The limiting elements of the embodiment of FIG. 8 may be combined-conveniently with the clamp of FIGS. 6 and 7. The latter clamp elements are threadably linked to the pivot pin so that the pin must rotate therewith, making it simple to extend the pin and to fix a limit arm thereto. The nature of the stop on the cover permits wide Variance in design Without affecting function.

FIG. 10 illustrates a cam clamp in accordance with the invention useful for retaining plates or sheets of material in place. In FIG. 10 a sheet 105 is supported by a work rest or bench 106. Vertical member 107 of the bench supports a pivot mount 108. A pivot pin 109 passed through the loop 110 of an eye bolt 111 and pivotally secures the eye bolt to the mount. A cam arbor 113 is threadably engaged with the upper portion of the eye bolt. A cam lobe 115 is secured upon the cam arbor and is rotatable about the horizontal axis of the arbor. A handle 116 attached to the cam lobe affords a lever by which the cam lobe may be revolved on the cam arbor to bring either of diametrically opposed cam surfaces 118, 119 to bear upon a clamping strap 121. The clamping strap impinges upon the work sheet, securing it to the work bench.

While only one cam lobe is shown, two lobes that are substantially identical and located on either side of the eye bolt may be used.

As in previous embodiments, the cam surfaces are the farthest projection of the cam periphery from the axis of rotation 123 of the cam arbor. In operation, the clamp is swung into clamping position about pivot pin 109 and the cam lobes are displaced along the eye bolt by rotation of the cam arbor on the threads. Handle 116 is utilized to bring a cam surface to bear upon clamp strap 121. If the clamping pressure is not correct, the clamp is unclamped and the position of the cam arbor on the eye bolt changed in the desired direction. Fine adjustments in increments related to a fraction of the pitch of the thread are possible because either carn surface 118 or 119 may alternatively bear upon the clamp strap, depending upon the number of half rotations of the cam arbor about the eye bolt.

The embodiment of FIG. 11 illustrates a compound cam clamp wherein two work plates 131, 132 are engaged by the clamping ends 134, 135 of a double-ended clamping strap 136. The clamping strap has an aperture 138.

through which a threaded eye bolt 139 of the clamp passes. An aperture 141 in a work bench 142 affords passage for the eye bolt upwardly from its pivot mount 144.

Preferably a cam arbor 146 adapted for rotation about the longitudinal axis of the eye bolt supports spaced cam lobes, such as the lobe 147. A handle 148 secured to either or both of the cam lobes, depending upon whether the lobes are fixed to the arbor or rotate about it, provides leverage to move the cam lobes into and from overcenter locked position.

The cam lobes of the embodiment of FIG. 11 are similar to those of the embodiments previously described and their configuration may be symmetrical or asymmetrical with respect to the axis of the cam arbor, depending upon the type and degree of fine adjustment desired.

The illustrative embodiments described heretofore are representative of only a few of those possible within the scope of the invention. For instance, as shown in FIG. 12, the previously described limit arm may comprise a square shank 151, slidable in a broached hole 152 through the extending portion 103 of the clamp pivot pin. A bevelled latch 154, slightly larger than shank 151, on the extending end of portion 151 retains a compression spring 156 between the periphery of extending portion 103 and the latch. The straight side 158 of the latch strikes against limit surface 99 of cover stop rib 98 to limit outward motion of the clamp assembly. However, when the cover is replaced on the vessel and the clamp assemblies, with the limit arms, are swung inwardly, the bevelled surface 159 of latch 154 strikes the outer corner of rib 98 and depresses against spring 156 sufficiently to permit an associated clamp assembly to swing into the clearance slotof a tab 95 without raising the cover.

Also, the displacement differential of the opposed cam surfaces of a cam lobe from the transverse or cam arbor axis may vary from an increment equal to the thread pitch of the threaded member to one'equal to a small fraction of the thread pitch. Since the clamp may be reclamped after 180 of rotation about the threaded member, the preferred embodiment comprises a clamp with a cam lobe whose opposite cam surfaces are equidistant from the transverse axis. The relative displacement of the cam lobes with respect to the clamped surface when a halfthread adjustment is made is predicated upon the combined additive and subtractive displacements from reorientations of both the cam arbor and the alternative cam surfaces. The invention therefore affords many differing cam clamps useable with conventional equipment and giving fine adjustment of clamping pressure with mini mum operational steps. The scope of the invention, therefore, is defined by the appended claims rather than by the illustrative description and drawing set forth herein.

I claim:

1. A cam clamp for clamping a workpiece to a work rest and comprising a threaded member, means securing the threaded member to the work rest, a cam lobe secured to the threaded member, a first and a second cam surface on the lobe at diametrically opposed locations adapted to urge the workpiece into clamping relationship with the work rest, handle means adapted to turn the lobe about an axis extending transversely to the long axis of'the threaded member, means for limiting the turning of the lobe; the cam lobe being displaceable with respect to the work rest along the member axis such that the cam lobe may be moved to and from the workpiece, and rotatable with respect to the long axis of the threaded member such that the cam lobe may be displacedto the opposite side of the threaded member, the lobe being further rotatable about the axis transverse to the long axis of the threaded member such that the first and the second cam surfaces of the cam lobe may be brought alternatively into clamping relationship with the workpiece.

2. Clamping apparatus in accordance with claim 1 wherein the workpiece comprises a pressure vessel cover having a clearance notch at its rim adapted to receive a threaded member and contact surfaces against which the cam lobes bear; and wherein the work rest comprises a pressure vessel having an opening adapted to be sealed by the cover.

3. Apparatus in accordance with claim 2 wherein the workpiece comprises a clamp strap adapted to bear against a sheet of work material, said clamp strap having contact.

surfaces adapted to be impinged upon by the cam lobe surfaces.

4. A cam clamp for clamping. a workpiece to a work rest and comprising a threaded member, means securing the threaded member to the work rest, a cam lobe secured to the threaded member, a first and a second cam sur-,

face on the lobe at diametrically opposed locations adapted to urge the workpiece into clamping relationship with the work rest, handle means adapted to turn the lobe about an axis extending transversely to the long axis of the threaded member, means for limiting the turning I of the lobe; the cam lobe being displaceable with respect. 1 to the work rest along the member axis such that the cam lobe may be moved to and from the workpiece,.and ro-. tatable with respect to the long axis of the threaded member such that the cam lobe may be displaced to the opposite side of the threaded member, the lobe being further rotatable about the axis transverse to the long axis of the threaded member such that the first and the second canr surfaces of the cam lobe may be brought alternatively) into clamping relationship with the workpiece; the distance of the first cam surface of the cam lobe from the transverse axis differing from the like distance of the second cam surface by an increment related to the pitch of the thread of the threaded member. I

5. Clamping apparatus in accordance with claim 4 wherein the workpiece comprises a pressure vessel cover. having a clearance notch at its rim adapted to receive a 7. An over-center cam clamp for clamping a workpiece to a work rest and comprising a threaded member, means securing the threaded member to the work rest, a cam arbor engaging the threaded member, a cam lobe 0n the arbor at each end thereof on opposite sides of the threaded member, a first and a second cam surface on each lobe at diametrically opposed points each adapted alternatively to contact the workpiece in clamping relationship with the work rest, handle means adapted to turn the lobes. in unison about an axis of the cam arbor transverse to the long axis of the threaded member, and means for limiting the turning of the lobes once an over-center clamping position is reached; the cam arbor being thre-adably displaceable with respect to the work rest such thatthe cam lobes may be moved to and from the work piece,.and

rotatable with respect to the long axis of the threaded. member such that the cam lobes may be displaced to.

opposite sides of the threaded member; the cam lobes being further rotatable about the cam arbor axis such.

that the first and the second cam surfaces of a lobe may be brought alternatively into clamping relationship with the workpiece.

8. An over-center cam clamp for clamping a workpiece to a work rest and comprising a threaded member,

means securing the threaded member to the work rest, a cam arbor engaging the threaded member, a cam lobe on the arbor at each end thereof on opposite sides of the threaded member, a first and a second cam surface on each lobe at diametrically opposed points each adapted alternatively to contact the workpiece in clamping relationship with the work rest, handle means adapted to.

turn the lobes in unison about an axis of the cam arbor transverse to the long axis of the threaded member, and

means for limiting the turning of the lobes once an overcenter clamping position is reached; the cam arbor being threadably 'displaceable with respect to the work rest such that the cam lobes may be moved to and from the workpiece, and rotatable with respect to the long axis of the threaded member such that the cam lobes may be displaced to opposite sides of the threaded members; the cam lobes being further rotatable about the cam arbor axis such that the first and the second cam surfaces of a lobe may be brought alternatively into clamping relationship with the workpiece, the distance of the first cam surface of each lobe from the cam arbor axis differing from the like distance of the second cam surface by an increment related to the pitch of the thread of the threaded member.

9. An over-center cam clamp for clamping a cover in sealing relationship to a pressure vessel and comprising a threaded member, pivot means securing the threaded member to the vessel, a cam arbor engaged by the threaded member, the cam arbor being rotatable about the axis of the threaded member such that the cam arbor is displaced with respect to the pivot means, a similar cam lobe on each end of the cam arbor on either side of the threaded member, a first and a second cam surface on each cam lobe, said surfaces being diametrically opposed and adapted alternatively to bear against the cover to urge the cover into sealing relationship with the pressure vessel, means for rotating the cam lobes in unison with respect to the axis of the cam arbor, and means for rotating the cam lobes with respect to the axis of the threaded member such that the cam arbor and the lobes are displaced with respect to the pivot means securing the threaded member, both of said rotating means combining to adapt the cam lobes for clamping contact with the cover by either the first or the second surfaces of the cam lobes.

10. Clamping apparatus in accordance with claim 9 further comprising limit means pivotally synchronized with outward motion of the clamp lobes about the axis of the pivot means and adapted to limit such outward motion of the clamp lobes prior to removal of the cover from contact with the vessel.

11. Clamping apparatus in accordance with claim 9 wherein the first cam surface of each lobe is displaced from the cam arbor axis a distance differing from the like displacement of the second surface by an increment related to the pitch of the thread of the threaded member.

12. A pressure vessel cover clamp for use with a vessel having a pressure chamber with a plurality of clamp pivot mounts with pivot pins on the external wall of the pressure chamber at spaced intervals and a cover having limit stops exteriorly of the chamber walls, the cover clamp comprising .a cam clamp pivoting with the pin of a pivot mount, a limit arm fixed to the pivot pin so as to pivot outwardly in synchrouism with outward pivot motion of the cam clamp, an end on the limit arm remote from the pivot pin adapted to engage the limit stop on the cover when the cover is in contact with the pressure chamber, said limit arm precluding motion of the cam clamp outwardly beyond the rim of the cover when said cover is in contact with the pressure chamber, the relationship between the limit arm and the stop being such that lsufiicient displacement of the cover from the pressure chamber disengages the limit arm from the stop so that the cam clamp may be pivoted outwardly free of the cover.

13. In a pressure vessel having a pressure chamber and a cover having a rim extending outwardly beyond the external wall of the chamber, said wall having pivot mounts at spaced intervals about its periphery supporting cover clamps adapted to seat the cover against the chamber in sealing relationship, the combination comprising a limit arm adapted to pivot outwardly with the outward pivot motion of -a cover clamp, a stop on the cover rim adjacent the clamp adapted to engage the limit arm so as to limit the outward swing of the clamp beyond that position precluding removal of the cover, the extent of the stop in the direction of cover removal being such that outward swinging of the clamp is so limited until the cover is displaced in the direction of removal from the limit arm to disengage the limit arm from the stop.

14. A pressure vessel cover clamp for use with a vessel having a pressure chamber to whose external wall a plurality of clamp pivot mounts with pivot pins is fixed at spaced intervals and a cover having limit stops exteriorly of the chamber walls, the cover clamp comprising a cam clamp pivoting with the pivot pin of a clamp pivot mount, a limit arm shank, a transverse pivot pin hole receiving the shank in nonrotating slidable relationship, -a latch on an end of the limit arm shank remote from the pivot pin, said limit arm shank and latch comprising a limit arm secured to the pivot pin so as to turn outwardly in synchronism with outward pivot motion of the cam clamp, a contact surface on the limit arm latch adapted to engage a limit stop on the cover when the cover is in contact with the pressure chamber, the limit arm being adapted to preclude motion of the cam clamp outwardly beyond the rim of the cover when said cover is adjacent the pressure chamber, a compression spring loading the limit am away from the pivot pin and toward the cover, and a sloping surface on the limit arm latch oriented such that inward motion of the cam clamp and the limit arm from a position beyond the confines of the cover and vessel brings the latch into contact with the cover so as to depress the limit arm sufiiciently to allow the cam clamp to assume clamping position without displacing the cover from the vessel, the relationship between the limit arm and the cover limit stop then being such that sufiicient displacement of the cover from the pressure chamber disengages the limit arm from the stop so that the cam clamp may be pivoted outwardly free of the cover.

15. An over-center clamp for a pressure vessel and a cover having bearing surfaces for the clamp and comprising a threaded eye bolt, threaded means securing the eye bolt in pivotal relationship to the wall of the vessel, a cam arbor supported by the eye bolt, a cam lobe disposed on each end of the cam arbor and separated by the eye bolt, a handle mount fixed to each of the cam lobes such that the lobes rotate in unison, cover contacting rotation limiting surfaces on the handle mount, the handle mount and cam lobes being free to rotate with respect to the axis of the arbor and being rotatable in unison with the eye bolt about the axis thereof, said rotation turning the eye bolt with respect to the bolt mount and displacing the eye' bolt and the cam lobes secured thereto with respect to the opening of the vessel, and a first and a second cam surface on each cam lobe, said cam surfaces being diametrically opposed and each adapted to be brought alternatively into clamping contact with the cover.

16. Apparatus in accordance with claim 15 wherein the first and the second cam surfaces are displaced differing distances from the anbor axis, the distance differential between the first .and second surfaces being related to the pitch of the thread of the eye bolt.

No references cited.

LOUIS G. MANCENE, Primary Examiner, JAMES B, MARBERT, Examiner, 

1. A CAM CLAMP FOR CLAMPING A WORKPIECE TO A WORK REST AND COMPRISING A THREADED MEMBER, MEANS SECURING THE THREADED MEMBER TO THE WORK REST, A CAM LOBE SECURED TO THE THREADED MEMBER, A FIRST AND A SECOND CAM SURFACE ON THE LOBE AT DIAMETRICALLY OPPOSED LOCATIONS ADAPTED ON URGE THE WORKPIECE INTO CLAMPING RELATIONSHIP WITH THE WORK REST, HANDLE MEANS ADAPTED TO TURN THE LOBE ABOUT AN AXIS EXTENDING TRANSVERSELY TO THE LONG AXIS OF THE THREADED MEMBER, MEANS FOR LIMITING THE TURNING OF THE LOBE; THE CAM LOBE BEING DISPLACEABLE WITH RESPECT TO THE WORK REST ALONG THE MEMBER AXIS SUCH THAT THE CAM LOBE MAY BE MOVED TO AND FROM THE WORKPIECE, AND ROTATABLE WITH RESPECT TO THE LONG AXIS OF THE THREADED MEMBER SUCH THAT THE CAM LOBE MAY BE DISPLACED TO THE OPPOSITE SIDE OF THE THREADED MEMBER, THE LOBE BEING FURTHER ROTATABLE ABOUT THE AXIS TRANSVERSE TO THE LONG AXIS OF THE THREADED MEMBER SUCH THAT THE FIRST AND THE SECOND CAM SURFACES OF THE CAM LOBE MAY BE BROUGHT ALTERNATIVELY INTO CLAMPING RELATIONSHIP WITH THE WORKPIECE. 